1. Field of Invention
The present invention relates to a method for producing catalysts. More particularly, the present invention relates to a method for producing photocatalyst for water splitting reaction.
2. Description of Related Art
Currently, there are many studies with respect to the semiconductor photocatalyst which is used to assist the dissociation of water for producing hydrogen and oxygen by being excited by sun light or visible light. The semiconductor photocalayst includes indium vanadium oxide, indium tantalum oxide, indium niobium oxide, strontium titanate etc. Zhingng Zou et al. disclosed an indium niobium oxide semiconductor catalyst made by solid reaction (Chem. Phys. Lett., volume 332, pages 271-277, 2000), wherein the amount of nickel-oxide cocatalyst was 0.5 weight percent (wt. %) and the hydrogen production amount, under 300 watt xenon lamp, was 3.5 μmol/hour-gcat. In addition, Zou et al., in Nature (volume 414, pages 625-627, 2001), disclosed an indium-tantalum oxide semiconductor catalyst prepared by using solid reaction, wherein the amount of nickel-oxide cocatalyst was 1 wt. % and the hydrogen production amount, under the 300 watt xenon lamp, was 3.2 μmol/hour-gcat. Furthermore, Ye et al., in Chem. Phys. Lett. (volume 356, pages 221-226, 2002), disclosed an indium vanadium oxide semiconductor catalyst formed by using solid reaction, wherein the amount of nickel-oxide cocatalyst was 1 wt. % and the hydrogen production amount, under the 300 watt xenon lamp, was 6.35 μmol/hour-gcat. Moreover, Ye et al., in International Journal of Hydrogen Energy (volume 28, pages 651-655, 2003), mentioned that the amount of platinum supported on NiM2O6 (M=Nb or Ta) was 0.1 wt. % and the hydrogen production amount, under the 400 Watt mercury lamp, was 360 μmol/hour-gcat. with respect to the use of the NiNb2O6 catalyst and 520 μmol/hour-gcat. with respect to the use of the NiTa2O6 catalyst. Kudo et al. disclosed that 1 wt. % platinum was loaded on the strontium titanate while chromium and tantalum were doped into the strontium titanate and the hydrogen production amount, under the 300 watt xenon lamp, was 70 μmol/hour-gcat., wherein the ratio of the doped chromium to the total catalyst and the ratio of the doped tantalum to the total catalyst were 4 mol % respectively.
In American patent with the U.S. Pat. No. 4,332,650, an electrothermal chemical process was used to dissociate water into hydrogen and oxygen. Also, in American patent with the U.S. Pat. No. 4,391,680, a water decomposition and electrolysis were used to prepare sodium hydroxide or potassium hydroxide. Furthermore, in American patent with the U.S. Pat. No. 6,726,893B2, a thin film device and a method for operating the thin film device were used to decompose water to produce hydrogen and oxygen. In another American patent with the U.S. Pat. No. 6,838,413B2, by the use of the oxysulfide semiconductor photocalayst modified with platinum, the water is decomposed to produce hydrogen. However, the hydrogen production amount by using the methods and the catalysts disclosed in all the documents and the issued patents is not high. How to increase the yield of hydrogen production becomes the main task in the field of photocatalysis.